Vibrator



Jan. 27, 1942. H. BARTELS 2,270,921

I VIBR-ATOR Filed Oct. 5, 1959 A TTORN E Y.

Patented Jan. 27,1942

VIBRATOR Hans Bartels, Berlin, Germany, assignor to TelefunkenGesellschaft fiir Drahtlose Telegraphic m. b. 11., Berlin, Germany, acorporation of Germany Application October 5, 1939, SerialNo. 297,969 InGermany October 11, 1938 3 Claims.

Choppers serve the purpose of interrupting a direct current voltage andof feeding the'ensumg alternating voltage superposed upon the directcurrent voltage to a transformer. These choppers essentially consist ofa vibratory spring or blade which is fitted with contacts and is subJectto electromagnetic excitation. The frequency of operation of thesechoppers is roughly equal to the natural mechanical frequency inherentinthe vibratory spring.

The vibrations are maintained by way of an electromagnet the solenoid ofwhich is energized by a current which, as a general rule, is opened andclosed in synchronism with the chopper vibrations. Choppers may beexcited in various ways, that is, either the working contacts which areincluded in the main or series circuit may be used directly therefor orelse a distinct contact known as an exciter contact is used for the saidobject. In either case the circuitcontaining the exciting coil may beeither interrupted or else the coil is short-circuited.

The object of this invention is to reduce the exciting power of choppersof the kind hereinbefore mentioned. More particularly, according to theinvention accessory circuit elements are included in the circuit of theexciter coil which serve the purpose of occasioning a delay or lag inthe rise of the exciting current.

The invention shall now be described in more detail by reference to theappended drawing wherein Figure 1 illustrates a chopper arrangementincorporating certain features of the present invention; and, Figure 2is a graph used to describe the invention.

Referring to the drawing, Fig. 1 shows a fundamental diagram of achopper. I denotes the oscillable or vibratory spring or blade the end 2of which'is caused to vibrate opposite the magnet 3 in the plane of thedrawing. 4 denotes the working contacts, while 5 stands for the excitingcontact. For the sake of greater simplicity the excitation of theoscillatory process or the vibrating shall be described by reference toa chopper fitted with an exciting contact.

As the current is switched in, the vibratory spring I will be attractedby the magnet 3; in other words, the spring will be deflected to theleft-hand side in the plane of the drawing. In-

cidentally, the current is broken at contact 5, the.

spring flies back to a point beyond the neutral or median position onthe right-hand side. Then the same process and cycle as before recurs:As a result of the current being made at contact 5, the magnet 3 isre-energized with the consequence that the spring I is pulled ove1 againto the left-hand side.

It will be seen that a moment of attraction arises in the magnet 3during the deflection of the spring away from the median positiontowards the right-hand side, as a result of the closure of contact 5.However, the attraction or pull during the motion of the spring out ofthe median position up to the maximum amplitude to the right acts inopposition to the vibration and is thus undesirable. In fact, it is onlythe second part of the attraction which arises during the time elapsingbetween the maximum deflection to the right-hand side and the medianposition as a result of the closing of contact 5 which has a usefuleffect in so far as it boosts and aids the oscillation of the spring.Hence, it is only the difference in the useful work of the magnet thatis really active which lies between these two quarters of the period. Inother words, the chopper will be able to operate only if the magneticforces in these two times differ at least slightly from each other. As ageneral rule, this end is attained by making conditions so that duringthe first quarter period, as a result of the building up of the current,the magnetic force will not reach at once its crest value, and thatduring the second quarter period, as a result of the decay, the magneticforce is somewhat extended or prolonged.

By using the present invention a greater lag or delay in the building-upaction is obtained, in other words, as great a reduction as possible ofthe current during the first quarter-period of the spring, figured fromthe instant when the exciting current has just been made.

One means which has proved eminently adapted consists of aniron-saturated choke-coil included in the circuit of the excitingcontact. Fig. 1, for instance, shows such a choke-coil 6 with highlysaturated iron. The building-up action of an unsaturated choke-coil isrepresented in Fig. 2 by the solid-line graph I, while the same processof a highly saturated iron-cored choke-coil is indicated by graph 2, idenoting the current and t the time; It will be seen therefrom that thefact that the current is building up very slowly means an appreciablereduction in the working power of the magnet during the first quarterperiod of the spring vibration. The

choke-coil 8 may be built into a mechanical construction unit with theexciting coil 3, for instance, in such a way that the exciting windingis made to act at the same time as the choke winding, and. that anadditional closed core consisting of readily saturable material isbrought into the winding.

In addition to these non-linear circuit elements a delay in thebuilding-up period of the exciting current could be realized also by theaid of fourterminal networks, say, a coil 1 indicated in Fig. 1.

For the purpose of suppression of sparking, as known in the art acondenser may be out between the poles of the exciting contact.

I claim:

1. In a circuit interrupter including a vibrator and a magnetic drivingcircuit for said vibrator, means in said exciter circuit for appreciablydelaying the magnetic driving force applied to the vibrator to such anextent that it is mainly effective during travel of the vibrator in thedi rection of attraction of said magnetic force, said means comprisingiron in a portion of the exciter circuit so arranged that the ratio ofthe flux linking said circuit to current flowing therein diminishes asthe current approaches its maximum value whereby the effectiveinstantaneous value of circuit inductance of the exciter circuit isrelatively large for small currents and relatively small for largecurrents with the result that as compared to the rate of growth ofcurrent through a constant inductance of a value which is intermediatesaid large value and said small value of circuit inductance, the currentincreases more slowly at first and more rapidly thereafter.

2. In a circuit interrupter of the type provided with a vibratingelement and an exciting coil for driving said vibrating element, acircuit including a make and break switching device and said excitingcoil for periodically energizing the exciting coil, a choke coil in saidenergizing circuit in series with the exciting coil, said coil beingarranged to become highly saturated, a predetermined time interval aftereach make of the switching device, said interval of time beingsufficient to delay the magnetic driving force applied to the vibratorto such an extent that the driving force is mainly effective duringtravel of the vibrating element in the direction of attraction of themagnetic force.

3. The arrangement described in claim 2 wherein the exciting windingacts also as the choke winding and by that a closed core consist-- ingof readily saturable material is mounted within said exciting winding.

HANS BARTELS.

